Mount adapter and imaging device

ABSTRACT

A mount adapter includes: a camera cone having a length of adjusting a flange focal length between an imaging device provided with an imaging element and an interchangeable lens; a focus detection unit carrying out focus detection from a phase difference; an optical device separating an incident light from the interchangeable lens into an incident light of the imaging element and an incident light of the focus detection unit; and a correction information storage unit storing correction information used for correction of an error between the flange focal length and a distance from a mounting surface of the interchangeable lens to the focus detection unit.

BACKGROUND

The present disclosure relates to a mount adapter and an imaging device.

Although digital single-lens reflex cameras have widely spread rapidlyin recent years, they have not been able to meet a request for furtherreduction in size and weight of the body. This is considered asinevitable for a digital single-lens reflex camera to put a reflexmirror that switches an optical imaging path and an optical path for thefinder and a pentaprism that guides a subject image to the finder (OVF:optical view finder) in the camera body.

With that, by being provided with an electric view finder (EVF) insteadof an OVF, mirrorless digital single-lens cameras, which intendreduction in size and weight by eliminating the reflex mirror, haveappeared. However, a sub-mirror that guides an incident light to a focusdetection unit is eliminated from such a mirrorless digital single-lenscamera as well as the reflex mirror, thereby not being able to carry outfocus detection of a phase difference detection system by the cameramain body.

Since a mirrorless digital single-lens camera has a shortened flangefocal length compared to that of a digital single-lens reflex camera,interchangeable lenses used to be mountable to a digital single-lensreflex camera are difficult to be used on their own. With that, in orderto effectively utilize the interchangeable lens resources in the past,an interchangeable lens for a digital single-lens reflex camera ismountable to a mirrorless digital single-lens camera by being mediatedby a mount adapter.

Then, in order to make an interchangeable lens compliant with the phasedifference detection system mountable, there is proposed an imagingdevice having the mount adapter that is provided with a focus detectionunit of a phase difference detection system (for example, refer toInternational Publication No. 2008/099605).

SUMMARY

However, the proposed imaging device used to have a disadvantage ofincreasing an error of the AF (auto focus) sensor focal length desiredto be equivalent to the flange focal length by mounting a mount adapterto be an intermediate accessory between the camera body and theinterchangeable lens. The AF sensor focal length is a distance from themounting surface of the interchangeable lens to the AF sensor, and theerror of the AF sensor focal length becomes a factor for a decrease inthe accuracy of focus adjustment and a decrease in the quality of therecorded image.

It is desirable to provide a mount adapter and an imaging device thatprevent a decrease in the accuracy of focus adjustment due to an errorof an AF sensor focal length.

According to an embodiment of the present disclosure, a mount adapter isprovided with a camera cone, a focus detection unit, an optical device,and a correction information storage unit. The camera cone has a lengthof adjusting a flange focal length between an imaging device providedwith an imaging element and an interchangeable lens. The focus detectionunit carries out focus detection from a phase difference. The opticaldevice separates an incident light from the interchangeable lens into anincident light of the imaging element and an incident light of the focusdetection unit. The correction information storage unit storescorrection information used for correction of an error between theflange focal length and a distance from a mounting surface of theinterchangeable lens to the focus detection unit.

In addition, according to an embodiment of the present disclosure, animaging device is provided with an information acquisition unit, acorrection information storage unit, and a driving amount calculationunit. The information acquisition unit adjusts a flange focal lengthbetween an imaging device and an interchangeable lens and also acquires,from a mount adapter having a focus detection unit carrying out focusdetection by separating an incident light from the interchangeable lens,correction information that is used for correction of an error betweenthe flange focal length and a distance from a mounting surface of theinterchangeable lens to the focus detection unit stored in the mountadapter and focus information that is detected by the focus detectionunit. The correction information storage unit stores correctioninformation used for correction of an error between the flange focallength and a distance from the mounting surface of the interchangeablelens to an imaging element. The driving amount calculation unitcalculates a lens driving amount for focus adjustment from thecorrection information stored in the correction information storage unitand the correction information and the focus information acquired by theinformation acquisition unit.

According to the mount adapter and the imaging device above mentioned, adecrease in the accuracy of focus adjustment due to an error of the AFsensor focal length is prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a configuration example of an imaging system in anembodiment;

FIG. 2 illustrates a block configuration example of the imaging systemin the embodiment;

FIG. 3 illustrates a regulation example of an imaging device and a mountadapter in the embodiment;

FIG. 4 illustrates an example of a correction information table of themount adapter in the embodiment;

FIG. 5 illustrates an example of a correction information table of theimaging device in the embodiment;

FIG. 6 is a flowchart of correction information acquisition process inthe embodiment;

FIG. 7 is a flowchart of control value update process in the embodiment;

FIG. 8 illustrates a block configuration example of an imaging system inanother embodiment; and

FIG. 9 is a flowchart of correction information acquisition process inthe embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

A detailed description is given below to embodiments of the presentdisclosure with reference to the drawings.

Embodiment

Firstly, an overall configuration of an imaging system in an embodimentis described using FIG. 1. FIG. 1 illustrates a configuration example ofthe imaging system in the embodiment.

An imaging system 1 is provided with an imaging device (camera body) 2,a mount adapter 10, and a lens (interchangeable lens) 7. The imagingdevice 2 is a camera body of a mirrorless digital single-lens camerathat is intended to reduce size and weight by shortening a flange focallength than that of a digital single-lens reflex camera. The lens 7 isan interchangeable lens for a digital single-lens reflex camera, and itis difficult to be mounted directly to the imaging device 2 because ofthe different flange focal length. The lens 7 is sometimes difficult tobe mounted due to the interface different from the imaging device 2.

The mount adapter 10 is mounted between the imaging device 2 and thelens 7. The mount adapter 10 regulates the flange focal lengths thatdiffer in mirrorless digital single-lens cameras from digitalsingle-lens reflex cameras. Since the flange focal length of amirrorless digital single-lens camera is shorter than the flange focallength of a digital single-lens reflex camera, it is regulated to be aflange focal length compliant with the lens 7 by mounting the mountadapter 10.

The imaging device 2 is provided with a shutter 3, a backside LCD(liquid crystal display) 4, an imaging element 5, a mount 6, variousoperational units, such as other control devices, a battery, and arelease button, not shown, various sensors, such as a temperaturesensor, and the like. The imaging element 5 carries out imaging of asubject as well as an image output to make the backside LCD 4 functionas an EVF and focus detection of a contrast system by detecting a lightpassing through the shutter 3.

The mount 6 is a joint portion to mount the imaging device 2 to a lenscompliant with a mirrorless digital single-lens camera. The mount 6 hasa joint portion shape to hold a lens and also has a contact to input andoutput various types of information, such as focus detection information(for example, ranging information and the like) and aperture valueinformation, between the imaging device 2 and the lens.

The mount adapter 10 is provided with a mount 11, a mount 12, an AFsensor unit 13, a thin film mirror (pellicle mirror) 14, a camera cone15, and others like control devices, a display unit, various operationalunits, a temperature sensor, and the like, not shown. The mount adapter10 may also be equipped with a light transmissive lid portion (forexample, a protective glass, a filter, or the like) not shown in anopening on the side of the imaging device 2 and in an opening on theside of the lens 7. The lid portion prevents dust and dirt from enteringinside and also protects the AF sensor unit 13 and the thin film mirror14 from being damaged due to an external force.

The mount 11 is a joint portion to mount the mount adapter 10 to theimaging device 2. The mount 11 has a joint portion shape to be held bythe imaging device 2 and also has a contact to input and output varioustypes of information, such as focus detection information and aperturevalue information, between the imaging device 2 and the mount adapter10. The mount 12 is a joint portion to mount a lens compliant with adigital single-lens reflex camera to the mount adapter 10. The mount 12has a joint portion shape to hold a lens and also has a contact to inputand output various types of information, such as focus detectioninformation and aperture value information, between the imaging device 2and the lens.

The AF sensor unit (focus detection unit) 13 is configured to includeoptical members, such as a condenser lens, an IR (infrared) cut filter,an aperture mask, and a separator lens, and carries out focus detectionof a phase difference system by introducing a light guided from asubject to the AF sensor. The AF sensor unit 13 outputs focus detectioninformation used for focus adjustment, such as ranging information, forexample. The AF sensor unit 13 is equipped at a position to be an AFsensor focal length compliant with a flange focal length of a digitalsingle-lens reflex camera.

The thin film mirror 14 is an optical device to separate a light L1incident from the subject side (lens 7 side) into a light L2 incident tothe imaging element 5 and a light L3 incident to the AF sensor unit 13.The thin film mirror 14 is a fixed semi-transmissive thin film mirror,and for example, separates approximately 70% of the incident light L1into the light L2 incident to the imaging element 5 and approximately30% of the incident light L1 into the light L3 incident to the AF sensorunit 13.

The camera cone 15 is in an approximately cylindrical shape and has theAF sensor unit 13 and the thin film mirror 14 therein. The camera conelength of the camera cone 15 is, when mounted between the imaging device2 and the lens 7, a length to make the distance from the mountingsurface of the lens 7 to the imaging element 5 to be a flange focallength compliant with the lens 7. The camera cone 15 has the AF sensorunit 13 disposed on a folded optical path of the thin film mirror in thecamera cone.

In such a manner, by regulating the flange focal length, the mountadapter 10 enables the lens 7 compliant with a digital single-lensreflex camera to be mounted to the imaging device 2, which is amirrorless digital single-lens camera.

Even in a case that the interchangeable lens does not have an AF sensor,the mount adapter 10 has the AF sensor unit 13, thereby the imagingsystem 1 enables focus detection of a phase difference system.

In a case that the interchangeable lens neither has an AF sensor nor hasthe mount adapter 10 mounted thereto, the imaging device 2 carries outfocus detection of a contrast system. Accordingly, the imaging device 2carries out focus adjustment by switching focus detection of a phasedifference system and focus detection of a contrast system correspondingto the mount adapter 10 or the interchangeable lens connected to theimaging device 2.

The lens 7 is an interchangeable lens compliant with a digitalsingle-lens reflex camera. The lens 7 is provided with a mount 8 andalso is provided with a driving mechanism driving the lens, an apertureadjustment mechanism adjusting the aperture, a control unit controllingthe mechanism units, and the like.

The mount 8 is a joint portion to mount the lens 7 to a compliantdigital single-lens reflex camera. The mount 8 has a joint portion shapeto be held by a digital single-lens reflex camera and also has a contactto input and output various types of information, such as focusdetection information and aperture value information, between the lens 7and the digital single-lens reflex camera. The mount 8 also becomes ajoint portion to mount the lens 7 to the mount adapter 10. The mount 8can input and output various types of information, such as focusdetection information and aperture value information, with the mountadapter 10 as well, similar to a digital single-lens reflex camera. Theinput and the output of information between the lens 7 and the mountadapter 10 may also be carried out directly by the control units of eachother and may also be carried out via the control unit of the imagingdevice 2.

Next, a block configuration of the imaging system 1 in the embodiment isdescribed using FIG. 2. FIG. 2 illustrates a block configuration exampleof the imaging system in the embodiment.

The imaging device 2 is provided with a control unit 110, the shutter 3,the backside LCD (display unit) 4, the imaging element (imaging unit) 5,a storage unit (correction information storage unit) 111, a temperaturedetection unit 112, and an operation input unit 113. The control unit110 integrally controls the imaging device 2 and also inputs and outputsvarious types of information with a control unit 100 of the mountadapter 10 described later.

The storage unit 111 stores, in advance, correction information tocorrect an error between the actual flange focal length of the imagingdevice 2 and the design value. The storage unit 111 is configured with anon-volatile storage medium, such as a flash memory and an EEPROM(electrically erasable programmable ROM), for example, to hold thecorrection information even during power off. Although the correctioninformation is specifically a correction value, such as a lens shiftamount, it may also be an error numerical value from the flange focallength as long as it is information to correct the lens shift amountbased on an error. Since the error from the flange focal length of theimaging device 2 varies in association with the change in temperature,the correction information includes a plurality of items of informationcorresponding to the temperature. The temperature of the imaging device2 is detected by the temperature detection unit (temperature sensor)112.

The operation input unit 113 is a release button, other operationswitches, and the like, and it accepts operations to select and performa function included in the imaging system 1, such as an AF operation, anoperation of the shutter 3, and display switch. The backside LCD 4functions as an EVF and also carries out reproduction display ofphotographed images and user interface screen display for variousoperations. For example, user interface screen display carries outguidance display for an AF operation.

The mount adapter 10 is provided with the control unit 100, a storageunit (correction information storage unit) 101, a display unit 102, atemperature detection unit 103, an operation input unit 104, an AFdetection unit (AF sensor unit) 105, and an AF mechanism unit 106. Thecontrol unit 100 integrally controls the mount adapter 10 and alsoinputs and outputs various types of information with the control unit110 of the imaging device 2. The control unit 100 also inputs andoutputs various types of information with a control unit 120 of the lens7. The control unit 100 has a relay function in a case of transmittingvarious types of information to each other between the control unit 110and the control unit 120.

The storage unit 101 stores, in advance, correction information tocorrect an error between the sensor focal length of the AF detectionunit 105 and the design value of the flange focal length. The storageunit 101 is configured with a non-volatile storage medium, such as aflash memory and an EEPROM, for example, to hold the correctioninformation even during power off. Although the correction informationis specifically a correction value, such as a lens shift amount, it mayalso be an error numerical value from the flange focal length as long asit is information to correct the lens shift amount based on an error.Since the error from the sensor focal length of the mount adapter 10varies in association with the change in temperature, the correctioninformation includes a plurality of items of information correspondingto the temperature. The temperature of the mount adapter 10 is detectedby the temperature detection unit (temperature sensor) 103.

The operation input unit 104 is an AF operation button, other operationswitches, and the like, and it accepts operations to select and performa function included in the mount adapter 10, such as an AF operation, anoperation of the shutter 3, and display switch. The display unit 102carries out notification display of the AF detection state of the AFdetection unit 105. For example, the display unit 102 is an LED (lightemitting diode) and carries out guidance display of the AF detectionstate of the AF detection unit 105 as just focus, near focus, or farfocus.

The AF mechanism unit 106 is an actuator, such as a motor, and thedriving amount is controlled by the control unit 100. The AF mechanismunit 106 transmits a driving force by being mechanically connected tothe lens driving unit 121 of the lens 7 (driving force transmissionunit) and carries out focus adjustment by driving the lens of the lens7. At this time, the control unit 100 calculates the driving amount ofthe AF mechanism unit 106, calculated from the focus informationdetected by the AF detection unit 105, using the correction informationof the imaging device 2 and the correction information of the mountadapter 10.

The lens 7 is provided with the control unit 120 and the lens drivingunit 121. The control unit 120 integrally controls the lens 7 and alsoinputs and outputs various types of information with the control unit100 of the mount adapter 10. In a case that the lens 7 is provided withan aperture adjustment mechanism unit, an information display unit, andthe like, not shown, the control unit 120 controls them. The lens 7 mayalso be provided with a driving unit that drives the lens driving unit121, and in that case, the control unit 120 drives the driving unit byreceiving a direction for the driving amount after correction from thecontrol unit 100.

In such a manner, the imaging system 1 enables the imaging device 2 tobe mountable to the lens 7 compliant with a digital single-lens reflexcamera. Then, the imaging system 1 enables focus adjustment in which theinfluence of the flange focal length error accumulated in the imagingdevice 2 and the mount adapter 10 is reduced.

Next, a regulation example of the imaging system 1 in the embodiment isdescribed using FIGS. 3 through 5. FIG. 3 illustrates a regulationexample of an imaging device and a mount adapter in the embodiment. FIG.4 illustrates an example of a correction information table of the mountadapter in the embodiment. FIG. 5 illustrates an example of a correctioninformation table of the imaging device in the embodiment.

The imaging system 1 has a configuration, as described above, in whichthe imaging element 5 is provided in the imaging device 2 and the AFsensor unit 13 is provided in the mount adapter 10. Therefore, due tothe variation in dimension accuracy, variation upon treatment, and thelike, the imaging system 1 has an error from the flange focal length(design value) in each of the distance from the mounting surface of thelens 7 to the imaging element 5 and the distance from the mountingsurface of the lens 7 to the AF sensor unit 13. Since the imaging device2 and the mount adapter 10 are considered to be often shipped to themarket as independent commercial products respectively, it is difficultto regulate them in advance in combination of a specific imaging device2 and a specific mount adapter 10. Accordingly, depending on thecombination of an imaging device 2 and a mount adapter 10, the imagingsystem 1 is difficult to obtain sufficient accuracy of focus adjustment.

With that, the imaging system 1 can improve the accuracy of focusadjustment by carrying out regulation of storing, in advance, correctioninformation to correct an error from the flange focal length in each ofthe imaging device 2 and the mount adapter 10.

Firstly, in a case of measuring the error of the mount adapter 10, theimaging system 1 carries out focus detection using a reference chart 90by mounting the imaging device 2 and the lens 7 to the mount adapter 10.At this time, reference items are used for the imaging device 2 and thelens 7. Since a focal distance D, a flange focal length A, and a lengthB on the side of the imaging device in the flange focal length arealready given, a length C on the side of the mount adapter in the flangefocal length is to be measured. This does not match with (flange focallength A)−(length B on the side of the imaging device in the flangefocal length), which is an already given value (design value), in allcases and sometimes has an error. The storage unit 101 stores the errorvalue or a correction amount that corrects the error value as correctioninformation in correspondence with a temperature, which is anenvironmental condition during regulation. For example, as shown in amount adapter side correction information table 130, in an environmentat 20° C., the storage unit 101 measures dm20 in correspondence with 20°C. for storage. Although error measurement may be carried out at from 0°C. to 40° C., which is a temperature in a range of the condition of use,the measurement may also be obtained by applying it to the errorvariation relative to the given change in temperature.

Regarding the measurement of the length C on the side of the mountadapter in the flange focal length, focus detection is carried out forthe reference chart 90 with the AF sensor unit 13 to define the amountof adjustment desired for focus adjustment as an error. Regarding thecorrection information, the amount of adjustment desired for the focusadjustment is calculated from the shift (driving) of the lens.

Then, in a case of measuring the error of the imaging device 2, theimaging system 1 carries out focus detection using the reference chart90 by mounting the mount adapter 10 and the lens 7 to the imaging device2. At this time, reference items are used for the mount adapter 10 andthe lens 7. At this time, since the focal distance D, the flange focallength A, and the length C on the side of the mount adapter in theflange focal length are already given, the length B on the side of theimaging device in the flange focal length is measured. This does notmatch with (flange focal length A)−(length C on the side of the mountadapter in the flange focal length), which is an already given value(design value), in all cases and sometimes has an error. The storageunit 111 stores the error value or a correction amount that corrects theerror value in correspondence with a temperature, which is anenvironmental condition during regulation. For example, as shown in animaging device side correction information table 140, in an environmentat 20° C., the storage unit 111 measures db20 in correspondence with 20°C. for storage. Although error measurement may be carried out at from 0°C. to 40° C., which is a temperature in a range of the condition of use,the measurement may also be obtained by applying it to the errorvariation relative to the given change in temperature.

Regarding the measurement of the length B on the side of the imagingdevice in the flange focal length, focus detection is carried out forthe reference chart 90 with the AF sensor unit 13 to define the amountof adjustment desired for focus adjustment as an error. Regarding thecorrection information, the amount of adjustment desired for the focusadjustment is calculated from the shift (driving) of the lens.

Next, correction information acquisition process performed by thecontrol unit 100 of the mount adapter 10 is described using FIG. 6. FIG.6 is a flowchart of correction information acquisition process in theembodiment.

[Step S11]

The control unit 100 determines power application to the imaging system1. The power application to the imaging system 1 is determined by powersupply to the control unit 100. The control unit 100 goes on to step S14in a case that power application takes place, and goes on to step S12 ina case that power application does not take place (already in a state ofpower application).

The power application to the imaging system 1 may also be determined byreceiving power application notification from the control unit 110 ofthe imaging device 2. This allows the mount adapter 10 to detect powerapplication to the imaging device 2 in a state of mounting the mountadapter 10 to the imaging device 2 as well as power application, bymounting the mount adapter 10, in a state of applying power to theimaging device 2. In such a manner, the control unit 100 functions as apower application detection unit that detects power application to theimaging device 2 or a connection detection unit that detects connection(mounting) to the imaging device 2.

[Step S12]

The control unit 100 determines imaging preparation of the imagingsystem 1. The imaging preparation of the imaging system 1 is determinedby receiving imaging preparation notification from the control unit 110of the imaging device 2. The imaging preparation notification is, forexample in a case that the control unit 110 detects switching of theimaging mode of the imaging device 2 or a half press (AF operation) ofthe release button, a signal notifies the control unit 100 from thecontrol unit 110. The imaging preparation of the imaging system 1 isdetermined by that the control unit 100 receives an AF operation inputfrom the operation input unit 104 of the mount adapter 10. The controlunit 100 goes on to step S14 in a case of determining that imagingpreparation takes place, and goes on to step S13 in a case ofdetermining that imaging preparation does not take place. In such amanner, the control unit 100 functions as a reception unit that acceptsan AF operation (operation of starting the focus detection) of the mountadapter 10 and as an operation detection unit that detects an operationof starting the focus detection of the imaging device 2.

[Step S13]

The control unit 100 determines a change in temperature of the mountadapter 10. For example, in a case that there is a change in temperatureexceeding a predetermined threshold from the temperature at the time ofthe previous error acquisition, it determines that there is a change intemperature. The control unit 100 goes on to step S14 in a case ofdetermining that there is a change in temperature, and terminates thecorrection information acquisition process in a case of determining thatthere is no change in temperature.

The threshold may be variable in accordance with, for example, a focaldepth, and the threshold is set to be large in a case of a deep focaldepth and the threshold is set to be small in a case of a shallow focaldepth, thereby the correction frequency can be appropriate.

[Step S14]

The control unit 100 acquires adapter side correction information of themount adapter 10 from the mount adapter side correction informationtable 130 stored in the storage unit 101.

[Step S15]

The control unit 100 acquires imaging device side correction informationby requesting it to the imaging device 2. At this time, in response tothe acquisition request for the imaging device side correctioninformation from the control unit 100, the control unit 110 of theimaging device 2 acquires the imaging device side correction informationof the imaging device 2 from the imaging device side correctioninformation table 140 stored in the storage unit 111. In such a manner,the control unit 100 functions as an imaging device side correctioninformation acquisition unit that acquires the imaging device sidecorrection information of the imaging device 2. The control unit 110notifies the control unit 100 of the imaging device side correctioninformation thus acquired. In such a manner, the control unit 110functions as an imaging device side correction information output unitthat outputs the imaging device side correction information of theimaging device 2.

[Step S16]

The control unit 100 calculates a total correction amount from theadapter side correction information and the imaging device sidecorrection information thus acquired and stores it together with thetemperature at the time of acquisition in the storage unit 101 toterminate the correction information acquisition process. In such amanner, the control unit 100 functions as a correction amountcalculation unit that calculates a correction amount of lens driving forthe focus adjustment.

Next, control value update process performed by the control unit 100 ofthe mount adapter 10 is described using FIG. 7. FIG. 7 is a flowchart ofcontrol value update process in the embodiment.

[Step S21]

The control unit 100 acquires the total correction amount from thestorage unit 101.

[Step S22]

The control unit 100 acquires a control value of the AF mechanism unit106 for focus adjustment based on the focus detection carried out by theAF detection unit 105. The control value of the AF mechanism unit 106can be calculated by the control unit 100. In such a manner, the controlunit 100 functions as a driving amount calculation unit that calculatesa control value (driving amount) of the AF mechanism unit 106.

[Step S23]

The control unit 100 updates the control value by correcting the controlvalue based on the total correction amount to terminate the controlvalue update process.

In such a manner, when carrying out focus adjustment based on focusdetection of a phase difference system, the mount adapter 10 can preventa decrease in the accuracy of focus adjustment due to an error of the AFsensor focal length.

Another Embodiment

Next, an imaging system in another embodiment is described. Whereas thecalculation entity of the total correction amount is a mount adapter inthe embodiment described above, the other embodiment differs at thepoint to be an imaging device. In the detailed description in the otherembodiment, a description of the overall configuration of the imagingsystem is omitted unless otherwise specified to consider it to be sameas that in the embodiment described above.

A block configuration of an imaging system 50 in the embodiment isdescribed using FIG. 8. FIG. 8 illustrates a block configuration exampleof the imaging system 50 in the embodiment.

An imaging device 52 is provided with a control unit 210, a shutter 3, abackside LCD (display unit) 4, an imaging element (imaging unit) 5, astorage unit (correction information storage unit) 211, a temperaturedetection unit 212, and an operation input unit 213. The control unit210 integrally controls the imaging device 52 and also inputs andoutputs various types of information with a control unit 200 of a mountadapter 51 described later. The control unit 210 inputs and outputsvarious types of information with a control unit 220 of a lens 53. Thecontrol unit 210 has a relay function in a case of transmitting varioustypes of information to each other between the control unit 200 and thecontrol unit 220. For example, the control unit 210 acquires focusinformation detected by an AF detection unit 205 and correctioninformation stored in a storage unit 201 from the control unit 200. Atthis time, the control unit 210 functions as an information acquisitionunit that acquires information from the control unit 200.

The storage unit 211 stores, in advance, correction information tocorrect an error between the actual flange focal length of the imagingdevice 52 and the design value. The storage unit 211 is configured witha non-volatile storage medium, such as a flash memory and an EEPROM, forexample, to hold the correction information even during power off.Although the correction information is specifically a correction value,such as a lens shift amount, it may also be an error numerical valuefrom the flange focal length as long as it is information to correct thelens shift amount based on an error. Since the error from the flangefocal length of the imaging device 52 varies in association with thechange in temperature, the correction information includes a pluralityof items of information corresponding to the temperature. Thetemperature of the imaging device 52 is detected by the temperaturedetection unit (temperature sensor) 212.

The operation input unit 213 is a release button, other operationswitches, and the like, and it accepts operations to select and performa function included in the imaging system 1, such as an AF operation, anoperation of the shutter 3, and display switch. The backside LCD 4functions as an EVF and also carries out reproduction display ofphotographed images and user interface screen display for variousoperations. For example, user interface screen display carries outguidance display for an AF operation.

The mount adapter 51 is provided with the control unit 200, a storageunit (correction information storage unit) 201, a display unit 202, atemperature detection unit 203, an operation input unit 204, and an AFdetection unit (AF sensor unit) 205. The control unit 200 integrallycontrols the mount adapter 51 and also inputs and outputs various typesof information with the control unit 210 of the imaging device 52. Themount adapter 51 has a relay unit 206 that carries out informationtransmission between the control unit 210 and the control unit 220.

The storage unit 201 stores, in advance, correction information tocorrect an error between the sensor focal length of the AF detectionunit 205 and the design value of the flange focal length. The storageunit 201 is configured with a non-volatile storage medium, such as aflash memory and an EEPROM, for example, to hold the correctioninformation even during power off. Although the correction informationis specifically a correction value, such as a lens shift amount, it mayalso be an error numerical value from the flange focal length as long asit is information to correct the lens shift amount based on an error.Since the error from the sensor focal length of the mount adapter 51varies in association with the change in temperature, the correctioninformation includes a plurality of items of information correspondingto the temperature. The temperature of the mount adapter 51 is detectedby the temperature detection unit (temperature sensor) 203.

The operation input unit 204 is an AF operation button, other operationswitches, and the like, and it accepts operations to select and performa function included in the mount adapter 51, such as an AF operation, anoperation of the shutter 3, and display switch. The display unit 202carries out notification display of the AF detection state of the AFdetection unit 205. For example, the display unit 202 is an LED andcarries out guidance display of the AF detection state of the AFdetection unit 205 as just focus, near focus, or far focus.

The lens 53 is provided with the control unit 220, an AF mechanism unit221, and a lens driving unit 222. The control unit 220 integrallycontrols the lens 53 and also inputs and outputs various types ofinformation with the control unit 210 of the imaging device 52. In acase that the lens 53 is provided with an aperture adjustment mechanismunit, an information display unit, and the like, not shown, the controlunit 220 controls them. The control unit 220 drives the AF mechanismunit 221 by receiving a direction of the driving amount after correctionfrom the control unit 210. At this time, the control unit 210 calculatesthe driving amount of the AF mechanism unit 221 calculated from thefocus information detected by the AF detection unit 205 using thecorrection information of the imaging device 52 and the correctioninformation of the mount adapter 51. In this case, the control unit 210functions as a driving amount calculation unit that calculates a controlvalue (driving amount) of the AF mechanism unit 221.

The AF mechanism unit 221 is an actuator, such as a motor, and thedriving amount is controlled by the control unit 220. The AF mechanismunit 221 is mechanically connected to the lens driving unit 222 andcarries out focus adjustment by driving the lens.

In such a manner, the imaging system 50 enables the imaging device 52 tobe mountable to the lens 53 compliant with a digital single-lens reflexcamera. Then, the imaging system 50 enables focus adjustment in whichthe influence of the flange focal length error accumulated in theimaging device 52 and the mount adapter 51 is reduced.

Next, correction information acquisition process performed by thecontrol unit 210 of the imaging device 52 is described using FIG. 9.FIG. 9 is a flowchart of correction information acquisition process inthe embodiment.

[Step S31]

The control unit 210 determines power application to the imaging device52. The power application to the imaging device 52 is determined bydetecting power supply to the control unit 210. In such a manner, thecontrol unit 210 functions as a power application detection unit thatdetects power application to the imaging device 52. The control unit 210goes on to step S35 in a case that power application takes place, andgoes on to step S32 in a case that power application does not take place(already in a state of power application).

[Step S32]

The control unit 210 determines adapter mounting of the imaging device52. The control unit 210 detects the adapter mounting of the imagingdevice 52 by mounting notification from the control unit 200. In such amanner, the control unit 210 functions as a connection detection unitthat detects the adapter mounting (connection) of the imaging device 52.The control unit 210 goes on to step S35 in a case that the adaptermounting takes place, and goes on to step S33 in a case that the adaptermounting does not take place (already in a state of mounting).

[Step S33]

The control unit 210 determines imaging preparation of the imagingsystem 50. The imaging preparation of the imaging system 50 isdetermined based on an imaging preparation state detected by the controlunit 210. The imaging preparation state is, for example, a case that thecontrol unit 210 detects switching of the imaging mode of the imagingdevice 52 or a half press (AF operation) of the release button. Theimaging preparation of the imaging system 50 is determined by that thecontrol unit 210 receives imaging preparation notification from thecontrol unit 200. The imaging preparation notification is, for example,notified by that the control unit 200 receives an AF operation inputfrom the operation input unit 204 of the mount adapter 51. The controlunit 210 goes on to step S35 in a case of determining that imagingpreparation takes place, and goes on to step S34 in a case ofdetermining that imaging preparation does not take place. In such amanner, the control unit 210 functions as a reception unit that acceptsan AF operation (operation of starting the focus detection) of theimaging device 52 and as an operation detection unit that detects anoperation of starting the focus detection of the mount adapter 51.

[Step S34]

The control unit 210 determines a change in temperature of the imagingdevice 52. For example, in a case that there is a change in temperatureexceeding a predetermined threshold from the temperature at the time ofthe previous error acquisition, it determines that there is a change intemperature. The control unit 210 goes on to step S35 in a case ofdetermining that there is a change in temperature, and terminates thecorrection information acquisition process in a case of determining thatthere is no change in temperature.

The threshold may be variable in accordance with, for example, a focaldepth, and the threshold is set to be large in a case of a deep focaldepth and the threshold is set to be small in a case of a shallow focaldepth, thereby the correction frequency can be appropriate.

[Step S35]

The control unit 210 acquires imaging device side correction informationof the imaging device 52 from the imaging device side correctioninformation table 140 stored in the storage unit 211.

[Step S36]

The control unit 210 acquires mount adapter side correction informationby requesting it to the mount adapter 51. At this time, in response tothe acquisition request for the mount adapter side correctioninformation from the control unit 210, the control unit 200 of the mountadapter 51 acquires the mount adapter side correction information of themount adapter 51 from the mount adapter side correction informationtable 130 stored in the storage unit 201. In such a manner, the controlunit 210 functions as a mount adapter side correction informationacquisition unit that acquires the mount adapter side correctioninformation of the mount adapter 51. The control unit 200 notifies thecontrol unit 210 of the mount adapter side correction information thusacquired. In such a manner, the control unit 200 functions as a mountadapter side correction information output unit that outputs the mountadapter side correction information of the mount adapter 51.

[Step S37]

The control unit 210 calculates a total correction amount from the mountadapter side correction information and the imaging device sidecorrection information thus acquired and stores it together with thetemperature at the time of acquisition in the storage unit 211 toterminate the correction information acquisition process. In such amanner, the control unit 210 functions as a correction amountcalculation unit that calculates a correction amount of lens driving forthe focus adjustment.

In such a manner, when carrying out focus adjustment based on focusdetection of a phase difference system, the imaging device 52 canprevent a decrease in the accuracy of focus adjustment due to an errorof the AF sensor focal length.

The control units 100, 110, and 120 described in the former embodimentand the control units 200, 210, and 220 described in the latterembodiment are controlled by a CPU (central processing unit). The CPU isconnected to a RAM (random access memory), a ROM (read only memory), acommunication interface, and an input and output interface via a bus.

In the RAM, at least a part of OS (operating system) programs andapplication programs to be performed by the CPU is stored temporarily.In the RAM, various types of data desired for process by the CPU arestored. In the ROM, OS programs and application programs are stored. Thecommunication interface is connected to other control units viacommunication lines.

The input and output interface is connected to the respective input andoutput units. With the hardware configuration as described above, theprocess functions of the embodiments can be realized.

Each control unit can also be configured to respectively include amodule composed of a FPGA (field programmable gate array), a DSP(digital signal processor), or the like, and can also be configured notto have a CPU. In that case, each control unit is provided with arespective non-volatile memory and stores a firmware of the module. Thefirmware can be written in the non-volatile memory via a portablerecording medium or a communication interface. In such a manner, eachcontrol unit can also be updated with a firmware by rewriting thefirmware stored in the non-volatile memory.

A variety of modifications can be made to the embodiments describedabove without departing from the scope of embodiments.

Further, the embodiments described above can also be variously alteredand modified by those skilled in the art and they are not limited to theexact configuration and the applications described above.

The present disclosure contains subject matter related to that disclosedin Japanese Priority Patent Application JP 2010-184620 filed in theJapan Patent Office on Aug. 20, 2010, the entire contents of which arehereby incorporated by reference.

1. A mount adapter comprising: a camera cone having a length ofadjusting a flange focal length between an imaging device provided withan imaging element and an interchangeable lens; a focus detection unitcarrying out focus detection from a phase difference; an optical deviceseparating an incident light from the interchangeable lens into anincident light of the imaging element and an incident light of the focusdetection unit; and a correction information storage unit storingcorrection information used for correction of an error between theflange focal length and a distance from a mounting surface of theinterchangeable lens to the focus detection unit.
 2. The mount adapteraccording to claim 1, further comprising: a correction informationacquisition unit acquiring correction information, used for correctionof an error of the flange focal length on an imaging device side andstored in the imaging device, from the imaging device; and a correctionamount calculation unit calculating a correction amount of lens drivingfor focus adjustment from the correction information stored in thecorrection information storage unit and the correction informationacquired by the correction information acquisition unit.
 3. The mountadapter according to claim 2, further comprising a correction amountoutput unit outputting the correction amount to the imaging device. 4.The mount adapter according to claim 2, further comprising: a drivingamount calculation unit calculating a driving amount of an actuator bycorrecting with the correction amount; and a driving force transmissionunit transmitting a driving force of the actuator to the interchangeablelens.
 5. The mount adapter according to claim 2, further comprising apower application detection unit detecting power application to theimaging device, wherein the correction amount calculation unitcalculates the correction amount based on the detection of the powerapplication to the imaging device.
 6. The mount adapter according toclaim 2, further comprising a connection detection unit detectingconnection to the imaging device, wherein the correction amountcalculation unit calculates the correction amount based on the detectionof the connection to the imaging device.
 7. The mount adapter accordingto claim 2, further comprising a temperature detection unit detecting atemperature, wherein the correction information storage unit stores thecorrection information corresponding to the temperature.
 8. The mountadapter according to claim 7, further comprising a reception unitaccepting a starting operation of the focus detection, wherein thecorrection amount calculation unit calculates the correction amountbased on the acceptance of the starting operation of the focus detectionby the reception unit.
 9. The mount adapter according to claim 7,further comprising an operation detection unit detecting a startingoperation of the focus detection in the imaging device, wherein thecorrection amount calculation unit calculates the correction amountbased on the detection of the starting operation of the focus detectionin the operation detection unit.
 10. The mount adapter according toclaim 1, wherein the optical device is a semi-transmissive thin filmmirror, and the focus detection unit is disposed in a folded opticalpath of the thin film mirror in the camera cone.
 11. The mount adapteraccording to claim 1, further comprising a display unit displaying afocus detection state by the focus detection unit.
 12. An imagingdevice, comprising: an information acquisition unit, adjusting a flangefocal length between an imaging device and an interchangeable lens, andalso acquiring, from a mount adapter having a focus detection unitcarrying out focus detection by separating an incident light from theinterchangeable lens, correction information that is used for correctionof an error between the flange focal length and a distance from amounting surface of the interchangeable lens to the focus detection unitstored in the mount adapter and focus information that is detected bythe focus detection unit; a correction information storage unit storingcorrection information used for correction of an error between theflange focal length and a distance from the mounting surface of theinterchangeable lens to an imaging element; and a driving amountcalculation unit calculating a lens driving amount for focus adjustmentfrom the correction information stored in the correction informationstorage unit and the correction information and the focus informationacquired by the information acquisition unit.
 13. The imaging deviceaccording to claim 12, further comprising a power application detectionunit detecting power application to the imaging device, wherein thedriving amount calculation unit calculates the lens driving amount basedon the detection of the power application to the imaging device.
 14. Theimaging device according to claim 12, further comprising a connectiondetection unit detecting connection to the mount adapter, wherein thedriving amount calculation unit calculates the lens driving amount basedon the detection of the connection to the mount adapter.
 15. The imagingdevice according to claim 12, further comprising a temperature detectionunit detecting a temperature, wherein the correction information storageunit stores the correction information corresponding to the temperature.16. The imaging device according to claim 15, further comprising areception unit accepting a starting operation of the focus detection,wherein the driving amount calculation unit calculates the lens drivingamount based on the acceptance of the starting operation of the focusdetection by the reception unit.
 17. The imaging device according toclaim 15, further comprising an operation detection unit detecting astarting operation of the focus detection in the mount adapter, whereinthe driving amount calculation unit calculates the lens driving amountbased on the detection of the starting operation of the focus detectionin the operation detection unit.